Long-Term Debt, Financing and Capital Lease Obligations (Narrative) (Details)	1 Months Ended				9 Months Ended
	Nov. 06, 2018 USD ($)	Feb. 28, 2017	Oct. 31, 2016 USD ($)	May 31, 2016 USD ($)	Dec. 31, 2018 USD ($) site years tranche	Dec. 31, 2017 USD ($)	Dec. 31, 2019	Nov. 26, 2018 USD ($)	Nov. 01, 2018 USD ($)	Oct. 01, 2018 USD ($)	Jun. 01, 2018	May 31, 2018	Mar. 31, 2018 USD ($) site	Feb. 20, 2018	Oct. 31, 2017 USD ($)	Feb. 02, 2017 USD ($)
Schedule of Capitalization, Long-term Debt [Line Items]
Long-term Debt, Gross								$ 7,100,000,000								$ 6,000,000,000
Long-term debt issued by 100% owned subsidiary and is fully and unconditionally guaranteed by the parent					$ 21,600,000,000
Interest Costs Capitalized					54,000,000	$ 42,000,000
Cash interest payments					1,900,000,000
Redeemable notes					30,300,000,000
Principal amount of notes with the right to require the Company to repurchase on change of control					24,100,000,000
Current portion of long-term debt, financing and capital lease obligations					3,596,000,000								$ 3,429,000,000
Maximum Funding Limit					$ 4,500,000,000
Receivables Facility, maximum amount available based on receivables sold to investors, percent					50.00%
Receivables Facility, Amount Outstanding					$ 3,300,000,000
Receivables Facility, Amount of Funds Available					131,000,000					$ 1,300,000,000
Receivables Facility, repayments	$ 2,000,000,000
Maximum Funding Limit, increase					200,000,000
Receivables Facility, Amount Drawn on Facility					5,100,000,000
Sale Leaseback Transaction, Cumulative Lease Payments					$ 4,200,000,000
Long-term Debt, Percentage Bearing Variable Interest, Amount																250
Number of cell sites leased back | site					1,750								3,000
Term in years for cell sites leased back renewal options | years					20
Payments for (Proceeds from) Businesses and Interest in Affiliates				$ 181,000,000
Ratio Of Total Indebtedness To Adjusted EBITDA					2.5
Financing Receivable, Net					$ 894,000,000								$ 1,149,000,000
Installment Lease Receivables, Net Book Value					6,700,000,000
Capital Lease Obligations [Member]
Schedule of Capitalization, Long-term Debt [Line Items]
Long-term Debt, Gross					310,000,000								686,000,000
Tower financing [Member]
Schedule of Capitalization, Long-term Debt [Line Items]
Sale Leaseback Transaction, Net Book Value					$ 118,000,000
Minimum [Member] | Capital Lease Obligations [Member]
Schedule of Capitalization, Long-term Debt [Line Items]
Debt Instrument, Interest Rate, Stated Percentage					2.35%
Maximum [Member] | Capital Lease Obligations [Member]
Schedule of Capitalization, Long-term Debt [Line Items]
Debt Instrument, Interest Rate, Stated Percentage					12.00%
Spectrum Assets [Member]
Schedule of Capitalization, Long-term Debt [Line Items]
Concentration Risk, Percentage			14.00%
Shentel [Member] | Capital Lease Obligations [Member]
Schedule of Capitalization, Long-term Debt [Line Items]
Long-term Debt, Gross					$ 118,000,000
Delcredere / Ducroire (D/D) Secured Equipment Credit Facility [Member] | Line of Credit [Member]
Schedule of Capitalization, Long-term Debt [Line Items]
Aggregate principal amount line of credit					250,000,000	$ 150,000,000
Repayments of Lines of Credit					40,000,000
Line of Credit Facility, Amount Outstanding					119,000,000
K-sure Secured Equipment Credit Facility [Member] | Line of Credit [Member]
Schedule of Capitalization, Long-term Debt [Line Items]
Aggregate principal amount line of credit					750,000,000
Repayments of Lines of Credit					$ 75,000,000
Number of tranches | tranche					3
Proceeds from Lines of Credit					$ 156,000,000
Line of Credit Facility, Amount Outstanding					275,000,000
Finnvera Secured Equipment Credit Facility [Member] | Line of Credit [Member]
Schedule of Capitalization, Long-term Debt [Line Items]
Aggregate principal amount line of credit															$ 800,000,000
Repayments of Lines of Credit					54,000,000
Line of Credit Facility, Amount Outstanding					120,000,000
Export Development Canada Agreement [Member] | Line of Credit [Member]
Schedule of Capitalization, Long-term Debt [Line Items]
Line of Credit Facility, Amount Outstanding													300,000,000
Export Development Canada Agreement [Member] | Tranche three and four [Member] | Line of Credit [Member]
Schedule of Capitalization, Long-term Debt [Line Items]
Line of Credit Facility, Amount Outstanding					300,000,000
Secured Revolving Bank Credit Facility expires in Feb 2021[Member] [Member] | Secured term loan [Member]
Schedule of Capitalization, Long-term Debt [Line Items]
Repayments of Lines of Credit					30,000,000
Line of Credit Facility, Amount Outstanding					3,900,000,000
Secured Revolving Bank Credit Facility expires in Feb 2021[Member] [Member] | Revolving Credit Facility [Member]
Schedule of Capitalization, Long-term Debt [Line Items]
Aggregate principal amount line of credit																$ 2,000,000,000
Line of Credit Facility, Remaining Borrowing Capacity					1,900,000,000
Line of Credit Facility, Amount Outstanding					0								0
Ratio Of Total Indebtedness To Adjusted EBITDA																4.8
Ratio Of Total Indebtedness To Adjusted EBITDA, Minimum																3.5
Secured Revolving Bank Credit Facility expires in Feb 2021[Member] [Member] | Letter of Credit [Member]
Schedule of Capitalization, Long-term Debt [Line Items]
Letters of Credit Outstanding, Amount					105,000,000
Sprint Nextel Corporation [Member] | Secured term loan [Member]
Schedule of Capitalization, Long-term Debt [Line Items]
Long-term Debt, Gross								$ 1,100,000,000								$ 4,000,000,000
Debt Instrument, Term		7 years
Line of Credit Facility, Amount Outstanding					5,030,000,000								3,960,000,000
Sprint Nextel Corporation [Member] | Senior Notes [Member]
Schedule of Capitalization, Long-term Debt [Line Items]
Long-term Debt, Gross					4,780,000,000								4,980,000,000
Current portion of long-term debt, financing and capital lease obligations					200,000,000
Debt Instrument, Interest Rate, Stated Percentage			9.25%
Sprint Nextel Corporation [Member] | Guaranteed notes [Member]
Schedule of Capitalization, Long-term Debt [Line Items]
Long-term Debt, Gross					$ 1,000,000,000				$ 1,753,000,000				2,753,000,000
Debt Instrument, Interest Rate, Stated Percentage					9.00%
Sprint Nextel Corporation [Member] | Minimum [Member] | Senior Notes [Member]
Schedule of Capitalization, Long-term Debt [Line Items]
Debt Instrument, Interest Rate, Stated Percentage					6.00%
Sprint Nextel Corporation [Member] | Minimum [Member] | Guaranteed notes [Member]
Schedule of Capitalization, Long-term Debt [Line Items]
Debt Instrument, Interest Rate, Stated Percentage					7.00%
Sprint Nextel Corporation [Member] | Maximum [Member] | Senior Notes [Member]
Schedule of Capitalization, Long-term Debt [Line Items]
Debt Instrument, Interest Rate, Stated Percentage					11.50%
PRWireless HoldCo, LLC Secured Term Loan [Member] | Secured term loan [Member]
Schedule of Capitalization, Long-term Debt [Line Items]
Repayments of Lines of Credit					$ 1,000,000
Line of Credit Facility, Remaining Borrowing Capacity					14,000,000
Proceeds from Lines of Credit					6,000,000
Line of Credit Facility, Amount Outstanding					187,000,000								182,000,000
Spectrum Financing [Member] | Secured Debt [Member]
Schedule of Capitalization, Long-term Debt [Line Items]
Debt Instrument, Maximum Borrowing Capacity			$ 7,000,000,000
Debt Instrument, Additional Borrowings Available													3,900,000,000
Sprint Spectrum Co LLC, Sprint Spectrum Co II LLC, Sprint Spectrum Co III LLC [Member] | Secured Debt [Member]
Schedule of Capitalization, Long-term Debt [Line Items]
Long-term Debt, Gross					6,344,000,000								7,000,000,000
Debt Instrument, Interest Rate, Stated Percentage			3.36%
Debt instrument face amount			$ 3,500,000,000
Debt Instrument, Term			5 years
Repayments of Debt					656,000,000
Secured Debt, Current					$ 875,000,000
Operating Leases, Future Minimum Payments Due			$ 3,500,000,000
Sprint Spectrum Co LLC, Sprint Spectrum Co II LLC, Sprint Spectrum Co III LLC [Member] | Minimum [Member] | Secured Debt [Member]
Schedule of Capitalization, Long-term Debt [Line Items]
Debt Instrument, Interest Rate, Stated Percentage					3.36%
Sprint Spectrum Co LLC, Sprint Spectrum Co II LLC, Sprint Spectrum Co III LLC [Member] | Maximum [Member] | Secured Debt [Member]
Schedule of Capitalization, Long-term Debt [Line Items]
Debt Instrument, Interest Rate, Stated Percentage					5.15%
Sprint Financing maturing 2021 [Member] | Secured Debt [Member]
Schedule of Capitalization, Long-term Debt [Line Items]
Long-term Debt, Gross					$ 2,400,000,000
Sprint Corporation [Member] | Senior Notes [Member]
Schedule of Capitalization, Long-term Debt [Line Items]
Long-term Debt, Gross					$ 12,000,000,000								$ 12,000,000,000
Debt Instrument, Interest Rate, Stated Percentage														7.625%
Sprint Corporation [Member] | Minimum [Member] | Senior Notes [Member]
Schedule of Capitalization, Long-term Debt [Line Items]
Debt Instrument, Interest Rate, Stated Percentage					7.13%
Sprint Corporation [Member] | Maximum [Member] | Senior Notes [Member]
Schedule of Capitalization, Long-term Debt [Line Items]
Debt Instrument, Interest Rate, Stated Percentage					7.88%
Spectrum Financing maturing 2025 [Member] | Secured Debt [Member]
Schedule of Capitalization, Long-term Debt [Line Items]
Debt Instrument, Interest Rate, Stated Percentage													4.738%
Debt Instrument, Additional Borrowings Available													$ 2,100,000,000
Spectrum Financing maturing 2028 [Member] | Secured Debt [Member]
Schedule of Capitalization, Long-term Debt [Line Items]
Debt Instrument, Interest Rate, Stated Percentage													5.152%
Debt Instrument, Additional Borrowings Available													$ 1,800,000,000
Wireless Service [Member]
Schedule of Capitalization, Long-term Debt [Line Items]
Purchase Commitment Allocation					22.00%						26.00%	26.00%
Installment Receivables [Member]
Schedule of Capitalization, Long-term Debt [Line Items]
Purchase Commitment Allocation					78.00%						18.00%	28.00%
Future lease receivables [Member]
Schedule of Capitalization, Long-term Debt [Line Items]
Purchase Commitment Allocation											56.00%	46.00%
Accounts and notes receivable, net
Schedule of Capitalization, Long-term Debt [Line Items]
Financing Receivable, Net					$ 675,000,000								995,000,000
Accounts and notes receivable, net | Wireless Services and Installment Receivables [Member]
Schedule of Capitalization, Long-term Debt [Line Items]
Financing Receivable, Net					2,500,000,000
Other assets
Schedule of Capitalization, Long-term Debt [Line Items]
Financing Receivable, Net					219,000,000								154,000,000
Other assets | Special purpose entity [Member]
Schedule of Capitalization, Long-term Debt [Line Items]
Financing Receivable, Net					204,000,000
Interest Rate Swap [Member] | Sprint Nextel Corporation [Member] | Secured term loan [Member]
Schedule of Capitalization, Long-term Debt [Line Items]
Derivative, Notional Amount																$ 2,000,000,000
Derivative Liability, Fair Value, Gross Liability					$ 31,000,000								$ 41,000,000
Derivative, Term of Contract					5 years
Scenario, Forecast [Member] | Secured Revolving Bank Credit Facility expires in Feb 2021[Member] [Member] | Revolving Credit Facility [Member]
Schedule of Capitalization, Long-term Debt [Line Items]
Ratio Of Total Indebtedness To Adjusted EBITDA							3.75
London Interbank Offered Rate (LIBOR) [Member] | PRWireless HoldCo, LLC Secured Term Loan [Member] | Secured term loan [Member]
Schedule of Capitalization, Long-term Debt [Line Items]
Debt Instrument, Basis Spread on Variable Rate					5.25%